Switch transformers over to source_span

pkg/observe/lib/transformer.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Code transform for @observable. The core transformation is relatively
 /// straightforward, and essentially like an editor refactoring.
 library observe.transformer;
 
 import 'dart:async';
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:barback/barback.dart';
 import 'package:source_maps/refactor.dart';
-import 'package:source_maps/span.dart' show SourceFile;
+import 'package:source_span/source_span.dart';
 
 /// A [Transformer] that replaces observables based on dirty-checking with an
 /// implementation based on change notifications.
 ///
 /// The transformation adds hooks for field setters and notifies the observation
 /// system of the change.
 class ObservableTransformer extends Transformer {
 
   final List<String> _files;
   ObservableTransformer([List<String> files]) : _files = files;
@@ skipping 29 matching lines @@
     return transform.primaryInput.readAsString().then((content) {
       // Do a quick string check to determine if this is this file even
       // plausibly might need to be transformed. If not, we can avoid an
       // expensive parse.
       if (!observableMatcher.hasMatch(content)) return;
 
       var id = transform.primaryInput.id;
       // TODO(sigmund): improve how we compute this url
       var url = id.path.startsWith('lib/')
             ? 'package:${id.package}/${id.path.substring(4)}' : id.path;
-      var sourceFile = new SourceFile.text(url, content);
+      var sourceFile = new SourceFile(content, url: url);
       var transaction = _transformCompilationUnit(
           content, sourceFile, transform.logger);
       if (!transaction.hasEdits) {
         transform.addOutput(transform.primaryInput);
         return;
       }
       var printer = transaction.commit();
       // TODO(sigmund): emit source maps when barback supports it (see
       // dartbug.com/12340)
       printer.build(url);
@@ skipping 338 matching lines @@
     token = token.next;
   }
   return token;
 }
 
 // TODO(sigmund): remove hard coded Polymer support (@published). The proper way
 // to do this would be to switch to use the analyzer to resolve whether
 // annotations are subtypes of ObservableProperty.
 final observableMatcher =
     new RegExp("@(published|observable|PublishedProperty|ObservableProperty)");